The primary objective of our long term research program is to study the interaction of ultrasound with tissue and to use this knowledge to establish new and improved techniques for ophthalmic diagnosis. Our recent research interests have involved ultrasonic tissue characterization; i.e., the noninvasive measurement of tissue acoustical properties and the correlation of these properties with tissue type and disease state. Specific goals for the current grant period include: 1. An extensive clinical evaluation of spectra-color ultrasonography using a real-time system recently developed in our laboratory. Spectra-color ultrasonography is a display technique developed by us for incorporating spectral information into a B-scan ultrasonogram. 2. An extensive tissue modeling study involving physical models as well as biological tissue in an attempt to understand in a more fundamental way the basis of a spectra-color display and the interaction of sound with tissue. 3. An investigation of other acoustical properties as possible parameters for tissue characterization. Although our present research program is directed toward clinical applications in ophthalmology, it should be clear that the results and basic principles of our investigation are applicable to other body regions and to any general biological structure.